Issue exploding duplicated border in Rhino 7.23

I have an issue since the last software update (7.23): when I use the command DupBorder to extract a silhouette, if I then explode the obtained curve to have (for example) the 4 edges of a like-squared face, it doesn’t split in the 4 main edges but it fragments into as many segment as the number of isocurves that originated the surface.

Here you may see what I mean: rhino issue while duplicating borders - YouTube (as shown at the end of the video, it doesn’t still happen while duplicating “edges” instead of “borders”, but this command is unusable when you have many surfaces with edges in common).

Is it possible to set Rhino to prevent this from happening and return to the previous setting?

Let me know, thanks.


Where did that surface come from? I can’t repeat this here. Are you sure that this is a single surface and not a polysurface (possibly imported from a mesh program or made from a polyline)? If it’s a polysurface, then the behavior is normal. Please post the file with the object otherwise.

Hi, yes, I’m sure it’s a surface and not a polysurface, it come from the tapered extrusion of an ellipse (here it’s just a part of the original surface, but it does the same also with the uncutted original one, and also with every moderate complex surface that has many isocurves).

I’ll share the file immediately. Thank you.

Here’s the file, inside you can find the surface used in the video, and also the uncutted one (the DupBorder command give me the same issue on every complex surface since the software update): WeTransfer - Send Large Files & Share Photos Online - Up to 2GB Free

I see this with a tapered extrusion of an ellipse… but not with a straight extrusion.

For me it’s different, it does exactly the same also with the simplest straight extrusion possible (a circle into a cylinder, I just tried): WeTransfer - Send Large Files & Share Photos Online - Up to 2GB Free

Here if I extrude a circle to a cylinder and then up the isocurves to 10, then DupBorder, the edges explode into 4 quarter circles. Not more.

However, in V6, the edges are already simplified and do not explode.

So it’s not about isocurves, but key-points that generated the curves (like quadrants of those circles).

But it’s still an annoying issue: it didn’t happen before the last update. On complex surfaces, using duplicate border was exactly the same as using the command duplicate edge right now

Yep, I definitely see something wrong in your file I downloaded. V6 DupBorder does not explode the edge curves of the full circular object at all - message “Cannot explode single curve segments.” - but V7 does into 364 separate elements. Definitely buggy. @pascal - one to check?

Your round surface is definitely a mess with 1093 control points around its circumference, but that still shouldn’t cause the issue.

Checking, thanks…

V6 sees a Nurbs curve, V7 a polycurve. My W.A.G is that this is related to V7 keeping the identity and structure, so to speak, of sub-curves in a curve, possibly.

RH-71030 DupBorder: Too explodeable


Do you have any solution? Otherwise, is it possible to download and reinstall a previous Rhino version (like 7.20, I’m pretty sure that version didn’t have this issue)?

I downgraded Rhino 7.20 (thanks to Rhino Customer Service) and it return normal as shown in this video:

To developers: please fix this problem in future releases.


RH-71030 is fixed in Rhino 7 Service Release 24

Thank you!